I’ve read, watched or heard somewhere that you can use the compositor to modify pictures and render them. not like the normal model-composite-render, kind of thing. I mean take an image and basically photoshop it. Is this possible and can you use this for BGE?
You can not use the compositor for the BGE. You could achieve similar effects using 2D filters, though they are much less visual than the compositing nodes. If the compositor was made to work in the BGE it would most likely be by converting the nodes to 2D filters.
unless your talking about the texture painting function in the uv editor, i agree with kupoman. but you could use a combination of the material nodes with the painting function inside the uv image editor to achieve the effect. Otherwise you should probably modify the pictures in a proper application like photoshop or gimp and then just move it back into your .blend file as an image texture
I think I misunderstood the original question. If you want to make changes to a texture in real time, look into the video texture module: http://www.blender.org/documentation/blender_python_api_2_69_1/bge.texture.html
Thanks a lot no, you understood it right the first time. I believe video texture is actually called Render-To-Texture? My main purpose is to use this for making main menu and side bars for a BGE game
In that case, you may want to look at either ovelay scenes, or BGUI (a library for crating menu’s and interfaces)